1. Field of the Invention
This invention relates to solar array panels and their manufacture and more particularly to electrostatically clean solar array (ECSA) panels and their manufacture.
2. Description of Prior Art
Certain space missions need solar arrays that do not affect the electromagnetic environment to allow for the uncorrupted operation of sensitive instruments. Solar arrays with exposed conductors both introduce and absorb current from the surrounding environment, and affect the shape of the plasma sheath that typically surrounds a solar array in earth orbit. Presently, solar arrays typically have electrical circuitry exposed to the extent that it interacts with the ambient plasma. This interaction affects the floating potential and particle trajectories surrounding the spacecraft, and in doing so the affected floating potential and particle trajectories may be sufficient in strength to influence scientific or otherwise sensitive mission readings.
The exposed circuitry of a solar array comprises primarily the solar cell interconnects and cell edges, although cell string terminations, panel diodes and terminal boards can also provide sites for electromagnetic field interactions. Typical solar cell arrays use individual cell-coverglass assemblies that have spacing between the cell-coverglass assemblies for electrical and thermomechanical reasons. Conventional solar panels use conductive-coated solar cell cover glasses. A typical coating material used conductive coating is Indium-Tin-Oxide (ITO). If the coverglasses use a conductive coating, the coverglasses must be electrically connected to each other and to the array structure to establish a ground plane. Even so, spacing between the coverglasses expose interconnects that interact with the ambient environment. For a typical solar panel, a large number of these exposed inter-cell and edge regions exist producing a collectively significant exposed area principally due to the relatively small size of cell-coverglass assemblies.
An electrostatically clean solar panel needs a method and means for covering these inter-cell and edge areas so as to create a contiguous ground plane on the front side and edges of the panel. Since electrical conductivity is already achieved on the array backside, a method and means for covering these inter-cell and edge areas is needed so as to create a contiguous ground plane on the front side and edges of the panel and thereby enable the panel that surrounds the solar cells to provide a grounded shield. Reliable electrical continuity of the grounded shield and insulation of the shield from the photovoltaic electrical circuit is critical. Accordingly, the method and means for covering these inter-cell and edge areas so as to create a contiguous ground plane on the front side and edges of the panel needs to minimize thermal mismatch stresses, use materials and processes that are qualified by similarity to existing techniques applied to solar panels, and minimize cost and complexity.
Embodiments of the present invention are disclosed including a preferred method of manufacturing an electrostatically clean solar array panel that includes a substrate having a perimeter surface and an array of solar cells, each with substantially rectangular cover glass sheets where the method includes the steps of first machining several substantially rectangular apertures into a flat, electrically conductive sheet with each aperture aligned with and undersized with respect to its matched coverglass sheet. The machined electrically conductive sheet, also termed a front side aperture shield and a frontside shield with apertures, is fabricated. The second step includes bonding the undersized portion about each aperture of the bottom side of the front side aperture shield to the top Bide portions nearest the edges of each aperture""s matched coverglass. The third step includes attaching a several edge clips to the front side aperture shield edges with the edge clips electrically and mechanically connecting the tops of the coverglasses to the perimeter surface solar panel substrate. The fourth step includes attaching the front side aperture shield, edge clips and substrate edges so as to produce a conductively grounded electrostatically clean solar array panel. Accordingly, a product by this disclosed process is an electrostatically clean solar array panel that includes a solar array panel having a perimeter surface and coverglasses, a front-side aperture shield of electrically conductive material, and edge clips mechanically and electrically connecting the coverglasses of said solar array to the solar panel perimeter substrate surface, whereby active power circuitry of the solar panel array is electromagnetically isolated.